The use of radio frequency (RF) signals, such as for providing wireless communication of voice, images, and data, for use in imaging, to provide sensing, etc., is commonplace to the point of nearly becoming ubiquitous. Due to various reasons, such as the availability of relatively unused spectrum, radiation providing penetration of a wide variety of materials, etc., the use of RF signals at higher and higher frequencies has become of interest. For example, the terahertz (THz) band from 0.3 THz to 3 THz is gaining increasing interest due to its potential for use with respect to various applications, such as imaging, spectroscopy, and high-speed wireless communication.
An antenna is an indispensable component of any RF radiating system to radiate out the signal generated from the signal sources or transmitters and of any RF receiving system to provide a signal to the receivers or signal sink from a radiated signal impinging on the antenna. However, antenna systems can be problematic with respect to their integration with many modern circuit configurations. For example, RF radiating and receiving systems are often provided in an integrated circuit configuration, such as to provide low power implementations, small form factors, system on chip (SOC) or system in package (SIP) solutions, etc. At frequencies as high as several tens to hundreds of GHz (e.g., sub-terahertz or terahertz frequencies), physical interconnection between on-chip circuitry and an off-chip antenna is often not feasible because of the severe loss, the high packaging cost, etc. Integrating antennas with the integrated RF circuitry (e.g., including an antenna system as part of the integrated circuit) likewise generally does not provide an acceptable solution. For example, the lossy silicon substrate and the metal/dielectric structure of the integrated circuit can impose an upper limit on the antenna performance in terms of radiation efficiency, gain, and bandwidth.
Although various techniques may be utilized to address the deficiencies in antenna implementations using conventional integrated circuit configuration, the existing techniques continue to result in an antenna configuration having undesired characteristics, such as unacceptably limited bandwidth, undesirable packaging costs, etc. For example, a microstrip patch antenna may be formed in an integrated circuit die or chip with ground plate above the substrate to shield the radiation from penetrating through the lossy silicon, wherein an antenna with a length of λg/2 (i.e., ½ wavelength antenna, where λg is the wavelength in the dielectric (here silicon)) can achieve a gain of approximately 6 dBi at 338 GHz. However, the −10 dB impedance bandwidth of this microstrip patch antenna configuration is within 5% because of the close proximity (e.g., approximately 10 μm) between the antenna element and the ground plate. As a further example, wafer thinning may be employed to reduce the substrate loss and thus to improve the radiation efficiency, although wafer thinning processes typically increase the fabrication costs dramatically. Further, a lens may be attached onto the substrate for backside radiation to increase the antenna gain. Such a lens is relatively costly and the antenna efficiency degrades as the chip area of the antenna increases. To address these issues, metal plated trenches may be implemented on the backside of the chip such that an antenna gain of approximately 3 dBi can be achieved. However, post-processing of the wafer, including backside slicing and metal filling, is required to implement the metal plated trenches, thus appreciably increasing the cost and complexity of manufacture of the circuit.